Interaction of intense laser pulses with hydrogen atomic clusters

The interaction between intense femtosecond laser pulses and hydrogen atomic clusters is studied by a simplified Coulomb explosion model. The dependences of average proton kinetic energy on cluster size, pulse duration, laser intensity and wavelength are studied respectively. The calculated results indicate that the irradiation of a femtosecond laser of longer wavelength on hydrogen atomic clusters may be a simple, economical way to produce highly kinetic hydrogen ions. The phenomenon suggests that the irradiation of femtosecond laser of longer wavelength on deuterium atomic clusters may be easier than that of shorter wavelength to drive nuclear fusion reactions. The product of the laser intensity and the squared laser wavelength needed to make proton energy saturated as a function of the squared cluster radius is also investigated. The proton energy distribution calculated is also shown and compared with the experimental data. Our results are in agreement with the experimental results fairly well.     

Probing structural and electronic properties of divalent metal Mgn+1 and SrMgn (n=2–12) clusters and their anions

Divalent metal clusters have received great attention due to the interesting size-induced nonmetal-to-metal transition and fascinating properties dependent on cluster size,shape,and doping.In this work,the combination of the CALYPSO code and density functional theory(DFT)optimization is employed to explore the structural properties of neutral and anionic Mg_n+1 and SrMgn(n=2-12)clusters.The results exhibit that as the atomic number of Mg increases,Sr atoms are more likely to replace Mg atoms located in the skeleton convex cap.By analyzing the binding energy,second-order energy difference and the charge transfer,it can be found the SrMg9 cluster with tower framework presents outstanding stability in a studied size range.Further,bonding characteristic analysis reveals that the stability of SrMg9 can be improved due to the strong s-p interaction among the atomic orbitals of Sr and Mg atoms.     

The angular momentum and parity projected multidimensionally constrained relativistic Hartree–Bogoliubov model

Nuclear deformations are fundamentally important in nuclear physics.We recently developed a multidimensionally constrained relativistic Hartree-Bogoliubov(MDCRHB)model,in which all multipole deformations respecting the V₄ symmetry can be considered self-consistently.In this work we extend this model by incorporating the angular momentum projection and parity projection to restore the rotational and parity symmetries broken in the mean-field level.This projected MDCRHB(p-MDCRHB)model enables us to connect certain nuclear spectra to exotic intrinsic shapes such as triangles or tetrahedrons.We present the details of the method and an exemplary calculation for ¹²C.We develop a triangular moment constraint to generate the triangular configurations consisting of three α clusters arranged as an equilateral triangle.The resulting ¹²C spectra are consistent with that from a triangular rigid rotor for large separations between the α clusters.We also calculate the B(E2)and B(E3)values for low-lying states and find good agreement with the experiments.     

Bergman Clusters Related to Bulk Amorphous Alloys and Quasi—crystals

The fcc Zr2Ni and MgCu2-type phases, as primary crystallization phases from some bulk amorphous alloys, have similar Bergman clusters in the first-two-shell atomic arrangement, which also appears in the hp MgZn2-type Laves phase coexisting with icosahedral quasi-crystals in the TiZrNi system. Therefore, Bergman cluster may be a bridge linking bulk amorphous alloys and quasi-crystals. The stability of the Bergman clusters Zr31Ni14, Mg31Cu14 and Mg18Zn27 can be reflected by density of states at the Fermi level and distribution of charge density on the plane of (100) calculated by local density functional theory.     

量子色动力学与核物理

概述了量子色动力学和中高能核物理在核散射、核子特性及核子－核子相互作用势方面的密切联系． The close relation between quantum chromodynamics (QCD) and the nuclear.physics in medium and high energy regions is briefly reviewed in some aspects such as nuclear scatterings, nueleon propertics as well as the interactions between nucleons.     

The AME2012 atomic mass evaluation (I). Evaluation of input data, adjustment procedures

This paper is the first of two articles (Part I and Part II) that presents the results of the new atomic mass evaluation, AME2012. It includes complete information on the experimental input data (including not used and rejected ones), as well as details on the evaluation procedures used to derive the tables with recommended values given in the second part. This article describes the evaluation philosophy and procedures that were implemented in the selection of specific nuclear reaction, decay and mass-spectrometer results. These input values were entered in the least-squares adjustment procedure for determining the best values for the atomic masses and their uncertainties. Calculation procedures and particularities of the AME are then described. All accepted and rejected data, including outweighed ones, are presented in a tabular format and compared with the adjusted values (obtained using the adjustment procedure). Differences with the previous AME2003 evaluation are also discussed and specific information is presented for several cases that may be of interest to various AME users. The second AME2012 article, the last one in this issue, gives a table with recommended values of atomic masses, as well as tables and graphs of derived quantities, along with the list of references used in both this AME2012 evaluation and the NUBASE2012 one (the first paper in this issue).     

Molecular Dynamics Simulation of Icosahedral Transformations in Solid Cu-Co Clusters

We study the icosahedral transformations of solid Cu Co clusters with different initial configurations by using molecular dynamics with the embedded atom method. It is found that the formation of symmetric icosahedral cluster is strongly related to the atomic number and initial configuration. The transformation originates from the surface into the interior of the cluster and is a structural change which is rapid and diffusionless. The icosahedral clusters with any composition and configuration, such as core-shell or three-shell duster, can be prepared by the means of solid-solid phase transition in bimetallic clusters.     

The AME2016 atomic mass evaluation (Ⅰ).Evaluation of input data;and adjustment procedures

This paper is the first of two articles(Part Ⅰ and Part Ⅱ) that presents the results of the new atomic mass evaluation,AME2016.It includes complete information on the experimental input data(also including unused and rejected ones),as well as details on the evaluation procedures used to derive the tables of recommended values given in the second part.This article describes the evaluation philosophy and procedures that were implemented in the selection of specific nuclear reaction,decay and mass-spectrometric results.These input values were entered in the least-squares adjustment for determining the best values for the atomic masses and their uncertainties.Details of the calculation and particularities of the AME are then described.All accepted and rejected data,including outweighted ones,are presented in a tabular format and compared with the adjusted values obtained using the least-squares fit analysis.Differences with the previous AME2012 evaluation are discussed and specific information is presented for several cases that may be of interest to AME users.The second AME2016 article gives a table with the recommended values of atomic masses,as well as tables and graphs of derived quantities,along with the list of references used in both the AME2016 and the NUBASE2016 evaluations(the first paper in this issue).     

Structure and property of metal melt Ⅲ—Relationship between kinematic viscosity and size of atomic clusters

The method of crucible rotating oscillation damping was employed to measure the kinematic viscosity of aluminum melt,and the curve of viscosity v versus temperature T from 935 to 1383 K was obtained.Besides,based on the calculation model of the evolution behavior of atomic clusters in liquid structure,the curve of atomic clusters size d versus temperature was obtained,and the calculated results are in good agreement with the experimental values.By analyzing experimental data,it was found that both the viscosity and the size of atomic clusters of aluminum melt are monodrome functions of temperature,and the relation between v(T) and d(T) is a linear function,i.e.,v = v 0 + K·d(T).This relation indirectly verifies the calculation model of the structural information of metal melt,which is of great significance for studying the relation between melt microstructure and macro-physical properties.     

A molecular dynamics study of the structural change differences between Au225 and Au369 clusters on MgO surfaces at low temperature

The differences in structural change between Au 225 and Au 369 clusters with their(111) facets supported on MgO(100) surfaces at 5 K are studied by using molecular-dynamics simulations with the atomic interchange potentials of the Au/MgO interface.The parameters are obtained from the ab initio energies using the Chen-Mo¨bius inversion method.Analyses of the pair distribution functions show that the two Au clusters use different deformation processes to adjust the distances between the interface atoms,owing to the misfit between the atom distances among the clusters and the substrates.The local structural changes are identified by atomic density profiles.     

超短脉冲强激光与团簇的相互作用

超短脉冲强激光与团簇的相互作用已被证明能够产生能量高达ＭｅＶ量级的高能离子和中子以及非常强的Ｘ射线辐射。广阔好原子团簇在超短脉冲强激光场的作用下的加热、电离和膨胀等机制,对这种相互作用的深入研究可能会对激光核聚变和Ｘ射线激光等应用领域产生重大影响。     

Universal property of the information entropy in atoms,nuclei and atomic clusters

The position- and momentum-space information entropies of the electron distributions of atomic clusters are calculated using a Woods-Saxon single particle potential. The same entropies are also calculated for nuclear distributions according to the Skyrme parametrization of the nuclear mean field. It turns out that a similar functional form S = a + blnN for the entropy as function of the number of particles N holds approximately for atoms, nuclei and atomic clusters. It is conjectured that this is a universal property of a many-fermion system in a mean field.     

Nuclear physics parallels in atomic cluster physics

This paper considers some examples of physical phenomena, manifesting themselves in electron scattering on atomic clusters, which are analogous with those known from nuclear physics. It is demonstrated that the electron diffraction plays an important role in the formation of both elastic and inelastic electron scattering cross sections. The essential role of the multipole plasmon excitations in the formation of electron energy loss spectra on clusters is elucidated. The main emphasis in the paper is laid on electron scattering on fullerenes and metal clusters, however, results are applicable to some extent to other types of clusters as well.     

Dynamic acceleration effects in explosions of laser-irradiated heteronuclear clusters

Intense, femtosecond irradiation of atomic and molecular clusters can initiate Coulomb explosions, generating particle energies sufficient to drive nuclear fusion. Last and Jortner have proposed, based on particle dynamics simulations, that heteronuclear clusters with a mixture of heavy and light ions will not explode by the simple, equilibrium Coulomb model but that dynamic effects can lead to a boosting of energy of the lighter ejected ions [Phys. Rev. Lett. 87, 033401 (2001)]. We present experimental confirmation of this theoretically predicted ion energy enhancement in methane clusters.     

Configurational transitions in processes involving metal clusters

We define the configurational state of an atomic system, e.g. a cluster of metal atoms, in terms of the nuclear coordinates of a specific local minimum of the potential energy surface (PES). Three types of configurational transitions are reviewed: chemical reactions, phase transitions in clusters and catalytic chemical processes involving clusters as catalysts. The analysis of the first two cases shows that although vibrational degrees of freedom of nuclei and configurational degrees of freedom are separable in lowest order, thermal motion of nuclei nevertheless influences the rate of a configurational transition. Therefore the height of the barrier that separates configurational states of the transition for the PES differs from the effective activation energy for this transition. For example, ignoring the thermal motion of atoms in Lennard-Jones clusters leads to a predicted value of their melting points twice which accounts for the thermal motion of atoms. Hence, in determining parameters governing configurational transitions, evaluation of the PES parameters, say, within the framework of DFT (density functional theory) must be augmented by information from molecular dynamics or some other method that accounts for nuclear motion.     

Tomographic reconstruction of multiple in-line electron holograms of realistic objects

In theoretical low energy electron point source microscopy, simulated holograms are made and used to reconstruct atomic clusters. In previous investigations, simple test clusters were used for convenience. In this paper we explore more realistic structures composed of a single type of atom such as diamond, graphite and Buckminsterfullerene--all of which consist of carbon atoms. We also examine clusters with two or more distinct atom types, including TiO(2), CuO, Pt(3)O(4), Ga(3)Pt(5), WC, MgCO(3), and MgO. Reconstructions from a single hologram do not give atomic resolution, and consist instead of 'spurious peaks' that are not located at atomic sites, as well as 'atomic peaks' close to atomic sites. Here we apply methods we developed previously to remove all spurious peaks. We show final reconstructions that consist only of atomic peaks located very close to atomic sites.     

The surfaces of compact systems: from nuclei to stars

While providing information from worlds separated by five-to-six orders of magnitude in dimensions and in energy, the pairing properties (electrical resistance and viscosity), the electromagnetic response (spectrum of colours), the resilience to stress (elasticity), the ability to deform (plasticity), etc., associated with clusters of atoms and with atomic nuclei have surprisingly similar properties, once the proper scalings are done, and demonstrate the many analogies that can be drawn between different finite many-body systems. These analogies can be further extended to cosmic and to customer tailored nanometre materials. Femtometre materials, like the inner crust of a neutron star (pulsar), are made out of the same protons and neutrons which make infinite nuclear matter. However in pulsars, protons and neutrons are arranged in the form of finite nuclei immersed in a sea of free neutrons. This is the reason why these celestial objects rotate, conduct heat, emit neutrinos, etc., very differently from infinite nuclear matter. In fact, these phenomena reflect the properties of the corresponding atomic nuclei which form the pulsar. Among these properties, those associated with the nuclear surface are most important. Nanostructured materials are made out of atoms as their more common forms, but the atoms are arranged in nanometre or sub-nanometre-size clusters, which become the constituent grains, or building blocks, of new materials like, e.g., C₆₀ fullerene. Because these tiny grains respond to light, mechanical stress and electricity quite differently from micron- or millimetre-sized grains, nanostructured materials display an array of novel attributes. At the basis of the new phenomena we find again the surface of the building blocks used to produce the new materials. A proper understanding of the interweaving of the single-particle motion with the static and dynamic deformations of the surface of finite many-body systems is likely to provide the key to open a whole new world of interdisciplinary research in such disparate fields as isolated atomic nuclei and clusters, new materials and compact stellar objects. The concepts and the experimental evidence needed to tool this key will be reviewed. Special emphasis will be set on the open questions still remaining to be answered to reach this goal.     

Particle-vibration coupling and many-particle correlation in nuclei

The formation of many-particle clusters within atomic nuclei as a result of the coupling between particle and vibrational modes has been investigated. Expressions for the formation probabilities have been obtained for different excitation energies of the nuclei, characterized by the nuclear temperature. The methods used in the analysis are those of the double-time temperature Green function and the Fredholm method of solving integral equations.     

Mössbauer spectroscopy,intracluster atomic mobility and thermodynamics of ultrafine oxide clusters

Summary Dynamic properties of ultrafine clusters of γ-Fe₂O₃ (ferric oxide, FO) were studied by M?ssbauer spectroscopy and by thermodynamic analysis. The data obtained for FO clusters allowed the conclusion that dynamic properties of clusters as well as the decrease of melting point and the appearance of a gap between freezing and melting points depend on intracluster atomic mobility. Intracluster atomic mobility in FO clusters was shown to increase by the action of surfactants which decrease intercluster interactions. The increase in intracluster atomic mobility was suggested to proceed via formation of a solid-liquid state. Paper presented at ICAME-95, Rimini, 10–16 September 1995.